ACEDB BNF & Parser

We intend to revisit the idea of mapping ACEDB models into
OPM (Object-Protocol Model) schemas in order to allow having
OPM `views' of ACEDB models. If nothing else, the OPM editor
provides graphical browsing and documentation capabilities
(postcript diagrams and latex document of classes) that may
help documenting ACEDB models.
We need for this an (independent) parser for ACEDB models based
on the latest ACEDB BNF syntax.